lockbyproc_example.txt   [plain text]

The following is a demonstration of the lockbyproc.d script,

   # lockbyproc.d
   dtrace: description 'lockstat:::adaptive-block ' matched 1 probe
   ^C
   
     pageout                                                       49438
     mysql-test-run                                                96414
     oracle                                                       149086
     sched                                                        220601

The above output shows that threads belonging to sched, the kernel, spent 
a total of 220 microseconds waiting for an adaptive mutex lock.




This example sampled for a longer interval,

   # lockbyproc.d
   dtrace: description 'lockstat:::adaptive-block ' matched 1 probe
   ^C

     init                                                         136228
     java                                                         371896
     oracle                                                       783402
     sched                                                       2315779
     mysqltest                                                   9428277
     mysql-test-run                                             10093658
     mysqld                                                     17412999
     fsflush                                                    19676738

Here we can see threads belonging to fsflush have spent a total of 19.7 ms 
waiting for an adaptive mutex. Note: it's not easy to say that it means a
19.7 ms delay in the completion of the fsflush program, as this value is 
the sum of the block times across all the threads. So it is possible that 
many threads were blocked at the same time, eg, it could have been 19 threads
blocked during the same 1 ms.